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Renewed Gravity Research Could Soon Yield Results

Posted by timothy on from the but-gravity-is-everywhere dept.

t482 writes "Dr. Michelle Thaller has a nice article describing the current thoughts on gravity. Why is it so weak? Detecting gravity waves has turned into a bit of a cottage industry. "We are close," says MIT physicist Rainer Weiss, a pioneer in gravity wave research for more than 30 years. "I think sometime in the next two or three years we will see something.""

70 of 89 comments (clear)

  1. Please explain by Rick+the+Red · · Score: 1

    I didn't know gravity was renewable. Heck, I didn't even know it wore out!

    --
    If all this should have a reason, we would be the last to know.
  2. 30 years and still no results? by Zemrec · · Score: 5, Funny

    Damn...that's gotta be depressing.

    (at the water cooler, 1973)
    "Hi, Bob, seen any gravity waves lately?"
    "Nope, but we're real close now."

    (in an instant message, 2003)
    "Hi, Bob, seen any gravity waves lately?"
    "Nope, but we're real close now."

    You gotta wonder what gets these people out of bed day in and day out.

    1. Re:30 years and still no results? by BobGarcia · · Score: 2, Funny

      The problem is that you can get too close. Get closer and you have to deal with other forces: weak, strong, midic(h)lorian, and IWOMM ("It works on my machine" -- the most mysterious and pissoffingous force of them all.)

      --
      Half of my words are lies. Neither you, nor I, nor anyone else, can tell which.
    2. Re:30 years and still no results? by Jahf · · Score: 2, Funny

      There should be a "+.5 Almost Funny" rating :)

      --
      It is more productive to voice thoughtful opinions (reply) than to judge (moderate) others.
    3. Re:30 years and still no results? by Tukla · · Score: 1

      Nah, that's easy. I just run "rm -rf /var/*" every morning.

      I wish my phone would stop ringing.

    4. Re:30 years and still no results? by Mr.+McGibby · · Score: 4, Funny

      Complaining about teaching undergraduate classes.

      --
      Mad Software: Rantings on Developing So
  3. Re:Heavy! by Anonymous Coward · · Score: 2, Informative

    Gravity waves are bread and butter on Slashdot

  4. Maligning Einstein?? by WTFmonkey · · Score: 4, Interesting
    Right, because it was Einstein's Theory of General Relativity, published in 1916, that proposed the existence of gravity waves -- ripples in the fabric of space-time that LIGO scientists hope to measure for the first time.

    Wrong, because even the greatest genius of the 20th century never dreamed that humans would build something sensitive enough to actually detect a passing gravity wave.

    Did Einstein ever actually say "We can never build a machine to detect these?" If not, then that's like saying that Plato was wrong because he never wrote about moon colonies. It just doesn't make sense. If he actually said, "We can never detect these things" then he's wrong. Otherwise he just didn't get around to thinking about it. Bad journalism.
    1. Re:Maligning Einstein?? by TRACK-YOUR-POSITION · · Score: 2, Insightful
      Heh, do you know the kind of things Plato said? Plato, like perhaps all great philosophers, is judged to be great by the originality of his ideas and arguments rather than how well such arguments correspond to either today's thinking or reality. Unless you think that everything is made of earth, air, fire, and water, or that slavery and fascism are good.

      Not that I'm arguing with the point your making, (I might not go so far as Bad journalism, though), but Plato struct me as a really humorous example, since he spent an awful lot of time saying things we now judge to be false.

    2. Re:Maligning Einstein?? by Thuktun · · Score: 1

      Heh, do you know the kind of things Plato said? Plato, like perhaps all great philosophers, is judged to be great by the originality of his ideas and arguments rather than how well such arguments correspond to either today's thinking or reality.

      In today's world, we call this a consultant.

    3. Re:Maligning Einstein?? by TRACK-YOUR-POSITION · · Score: 1

      Tee Hee

  5. And another thing by WTFmonkey · · Score: 3, Interesting
    At those levels, scientists say they should be able to detect gravitational radiation from the first moments of the universe -- relic signals from the first second of the Big Bang.
    I must be physics challenged. If there were waves created by the big bang, wouldn't they have moved away from the center much faster than the stuff that makes up our planet? Like 2 (3-d) ripples in a pond, one moving faster than the other? Or is this one of those "The universe is infinite and everything is moving away from everything else so there was no 'central location of the universe' because at the time of big bang the universe was only as big as the stuff was expanding" things. But.. but... if it's expanding, how is it infinite? If it's infinite, how is it expanding?

    I wish I could wrap my mind around these things, because it's fascinating as hell, I just can't quite fit it.

    1. Re:And another thing by Yokaze · · Score: 4, Interesting

      Space is finite, but has not borders and is expanding.

      The best likening I've heard of is the surface (2D) of a baloon.

      The surface of the baloon has no borders, you can go around it like you want. Still, its space is finite. And if you pump it up, the space is expanding.

      The mistake most people make in imagining the Big Bang is taking it literally. An explosion of material in space.
      The point is there was no space in which the explosion happened and neither was material. Space happened. Material came even later.

      --
      "Between strong and weak, between rich and poor [...], it is freedom which oppresses and the law which sets free"
    2. Re:And another thing by DrLudicrous · · Score: 1

      Space happens. Shit comes later.

    3. Re:And another thing by rwaldin · · Score: 3, Informative
      Well maybe, or maybe not. From Parallel Universes
      Space could be finite if it has a convex curvature or an unusual topology (that is, interconnectedness). A spherical, doughnut-shaped or pretzel-shaped universe would have a limited volume and no edges. The cosmic microwave background radiation allows sensitive tests of such scenarios [see "Is Space Finite?" by Jean-Pierre Luminet, Glenn D. Starkman and Jeffrey R. Weeks; Scientific American, April 1999]. So far, however, the evidence is against them. Infinite models fit the data, and strong limits have been placed on the alternatives.

      Personally, I prefer to think that this universe may not be infinite, but an infinite number of the infinitely many parallel universes are!
    4. Re:And another thing by Ruy-sun · · Score: 1

      I like your thoughts of there being infinite number of parallel universes. I belive there are infinite times that each time is a branching point for unlimited posible futures. In the end only one is chosen, but all are done. Though in this world only one action was taken in a parallel universes another event took place. So in the end all acions and reactions that are posible happen. And this will branch of agine and agine cousing limmitless posibilitys. *so the next time you deside to stop at a red light remiber in another world you ran it: in one you lived, in one you got a ticket, in one you went to the hospetle, in one you killed someone, in one you killed yourself

    5. Re:And another thing by LarryRiedel · · Score: 1
      If there were waves created by the big bang, wouldn't they have moved away from the center much faster than the stuff that makes up our planet?

      My impression is that at the moment of the "big bang" the universe was not a point-- it had some sort of volume-- there was a distance between two points inside it, and as it grew, that distance got bigger. Some light or gravity waves or whatever that was generated at the moment of the big bang has not yet gotten here from where it started-- it continues to arrive from places that were at increasingly greater distances from here at the moment of the big bang.

      Larry

    6. Re:And another thing by edgar_is_good · · Score: 2, Insightful

      The point is that the big bang happened everywhere at once - at least insofar as we're causally aware right now. The entire universe was incredibly hot, and then the space itself expands, so the universe becomes dilute, cools, galaxies form, etc. There was a recent result - the WMAP experiment - which sees the relic radiation from the big bang. But the light we see was emitted from 14 billion light years aware (14 billion years being the age of the universe) and is just getting here now. In another billion years, we'll still be seeing this radiation, but it will be sourced 15 billion light years away, but just getting here then. The fact that this radiation is isotropic to one part in 100000 is the best evidence that the _whole_ universe was hot and expanded. The gravity waves travel just like the light - we'll see the waves produced 14 billion light years away now. But the big bang wasn't a point in space, in which case you would have been right. This is a common misinterpretation (even among people who ought to know better)

    7. Re:And another thing by richie2000 · · Score: 1

      I like to think that in a parallell universe, the other me is getting it on with this incredibly hot Spanish girl I keep running into...

      --
      Money for nothing, pix for free
    8. Re:And another thing by Nyphur · · Score: 2, Interesting

      "Space in finite, but has not borders and is expanding."

      Think in terms of energy levels. If we take a perfect vacuum, a space in which nothing exists, there is no energy. Of course, even space isn't a perfect vacuum. Such a vacuum would be expected to be found somehwere outside the measurable distance of the universe. "Beyond the edge," as it were. Thinking in terms of energy levels, we can percieve matter to be the highest energy level. Matter being thought of as energy condensed and slowed to a stable coactive form is not a new idea, but it has been one of the most important principals of Quantum Phyiscs on such issues.
      Taking this as true, matter cannot exist as an energy level without energy levels bneath it being full, otherwise the matter would drop down to the lower energy level and release a tremendous ammount of energy in the process. This again, is not that new of a way of thinking. "Zero point" energy, as it is called, is the lowest order of energy. It has been proposed that if we could tap into zero point energy, we could effectively get limitless energy for free, zero point energy being essentially everywhere since if there is a place for anything to exist, that place must have energy levels higher than the zero point and thus the zero point energy levels must be there. Even in a total vacuum, zero point energy exists. However, the potential of "mining" zero point energy is not in the energy you get yourself from removing it. Indeed, it would probably require a tremendous input of power in order to remove zero point energy from an area of space. The theoretical potential which exists for mning zero point energy is the fact that once it is removed, all energy levels above it must drop to fill in the space. Thus, if you took some matter and in the space in which the matter existed, mined out the zero point energy, the matter would convert into a lower energy form than matter, having no energy level to be based on as matter itself. This would, in essence, convert the matter to energy, releasing a tremendous ammount of energy. It is said that the resulting explosion from removing a small potion of zero point energy from matter filled space would make the largest nuke look like a firecracker.

      This all said, we have to consider what exists at the "edge" of the universe. With amtter existing based on higher energy levels in places and no matter existing in others, it is reasonable to assume that the energy levels are concentrated towards some kind of central point and thus fade, the further you get from that point. The edge of the universe would then be an area which has few higher energy levels, eventually fading out into a point of having not even zero point energy. This point of not having zero point energy would result in a lack of space existing in the sense that we know it, making a final edge to the expanse of the universe. However, any matter approaching this edge would be converted to energy slowly as it passes the point where there is no energy level below matter in order that the amtter can remain matter. This means we can't actually send matter to the edge of the universe since it is of too high an energy order.
      The energy levels diffusing and expanding from the central point of highest energy level (the big bang point, if you like) to lower points of lower energy levels, which is essentially, the universe expanding.

      It's all just a theory of mine though.. pieced together from this and that. It works right in my head and I'll probably change it some time if I find out more on the subject.

      --
    9. Re:And another thing by WTFmonkey · · Score: 1
      Thanks for the answers. I guess the hardest part for me to grasp is the radiation part.

      Let's say I'm immortal for a minute. And let's say that we know how far it is from here to the furthest edge of teh universe, call it a godzillion light years. Will I stop seeing this radiation in a godzillion years (life age of the universe notwithstanding)? Seems like you would, because that initial whumph of radiation from that godzillion light years away, well there was nothing beyond that when

      *head explodes*

    10. Re:And another thing by edgar_is_good · · Score: 1

      Well, see, the big bang is reall the result of what's referred to as the reheating phase after the inflationary phase (in the current cosmology - let me not discuss the evidence for that right now). In the early universe, it is believed to be twisted and contorted and very irregular. Then some dynamics takes over a small patch an inflates it, expands it exponentially, fast enough, even, that two points that had been in causal contact before (i.e., capable of exchanging a light signal within the age of the universe) get separated out of causal contact.

      So they're separating faster than the speed of light, but only because the space itself is expanding so rapidly, not because they're moving in space so rapidly. This expansion dilutes the universe incredibly so it is essentially empty. This expansion was driven by an energy, which when the expansion stops, converts into heat and radiation. This is the big bang, and the entire (now huge and smooth) patch reheats simultaneously.

      So now we see that radiation as I explained before. Eventually we (meaning you, if you were immortal and didn't have to worry about the fate of the Earth, sun, etc) would eventually see the edge of that expanded patch, but that is not the end of space, just the end of that patch of the very early universe which got expanded. The universe could be finite outside of that patch, or could be infinite. There is a parameter which tells us the geometry, called Omega, and Omega>1 means closed, Omega1 means open. Omega =1 means flat, which essentially means infinite, but you have to be careful what you mean. Unfortunately or fortunately, this exponential expansion period changes omega so that it gets exponenentially close to 1, so we can't really tell if it is above or below. In fact, present measurements are that it is pretty close to one (which is what everyone sort of expected).

      Anyway, that's the quick version. The real answer to the question of "what's beyond the horizon"? (the farthest distance light could have travelled since the big bang/reheating ) is we don't have any way of knowing and there are a lot of possibilities.

    11. Re:And another thing by Nyphur · · Score: 1

      I'm not the best at phrasing things. If you stopped reading there, you made a big mistake. I went on to explain that een a perfect vacuum has "zero point" energy, known by many names. One of these names is "Vacuum energy" though that encompases more than jsut the lower level of zero point energy.
      Your impatience has cost you what might possibly have been a good read.

      --
    12. Re:And another thing by PDAllen · · Score: 1

      Space might be infinite - AFAIK, we don't know yet; general relativity doesn't help (it tells us about local properties of space, from which we can deduce some global properties, but both finite and infinite spaces are mathematically possible). For a simple finite analogy, the standard blowing-up-a-balloon thing works. For infinite space with expansion: what's meant isn't that space-now is bigger than space-past, if you look at the 'total area' (infinite, and infinite) but that wherever you look from, you find that (on average) everything is moving away from everything else. Simple 2-d example of infinite space which is expanding: space is the 2-d plane, and everything in it moves directly away from the origin at a speed linearly proportional to the distance from the origin. Simulate that on a computer, and you'll see it works. (note: AIUI, there are interesting effects that come into play in the GR equations if space is expanding, above and beyond the obvious stuff-moving; I'm not into that side of maths, though)

    13. Re:And another thing by Nyphur · · Score: 1

      Oh, actually, I notice what you mean there. ARGH, I wrote in a vacuum there is no energy and what I meant to write was matter, not energy. In a perfect vacuum there's no matter, not no energy.

      my appologies, what a stupid mistake.

      --
    14. Re:And another thing by Alsee · · Score: 1

      in a parallell universe, the other me is getting it on with this incredibly hot Spanish girl...

      The good news is that in an an infinite number of parallel universes, everything that CAN happen DOES happen somewhere. The bad news is that you are telepathetic in all universes, so it never happens anywhere. :)

      -

      --
      - - You can't take something off the Internet! That's like trying to take pee out of a swimming pool.
    15. Re:And another thing by nomel · · Score: 1

      I'm not very familiar with this subject...but...

      Was space a result of the big bang or something? Was distance? If not, then what do you call the stuff 10 miles from the first moments of the big bang? I'm sure it would have a name, even if it were nothing.

      Or, do you mean space, as in this definition?
      "The infinite extension of the three-dimensional region in which all matter exists." [dictionary.com].

      And, I'm confused by this your quote,
      "The point is there was no space in which the explosion happened and neither was material."
      I do make the mistake you mentioned, that's all I've ever learned. If there was no material, then where did it come from? Are you assuming that the universe didn't exist before this one (as in, there wasn't a universe that collapsed before it)?

      Thanks (please respond, I'm curriouse).
      -nomel

    16. Re:And another thing by nomel · · Score: 1

      I'm confused. If it was seen 14billion light years away, then what created it? If the whole universe was hot like you mention, then wouldn't there not be a specific point that you are talking about? What would create that point?

    17. Re:And another thing by dmatos · · Score: 1

      I kept reading. I like a good joke :)

      --

      It may look like I'm doing nothing, but I'm actively waiting for my problems to go away.
      --Scott Adams
    18. Re:And another thing by Yokaze · · Score: 1

      First of, I'm stating it like it is the truth. But in fact, it is a theory, which AFAIK is (or at least was) the most accepted one. Remember all what I say is limited by my lay-mans knowledge.

      > Was space a result of the big bang or something? Was distance?

      Excactly. So, at one point in time, 10 miles from anywhere could mean 10 times through the universe and back to where you started through a universe with a mile diameter.

      That is why there is a uniform background radiation, which are a reminiscence from the Big Bang.

      > If there was no material, then where did it come from? Are you assuming that the universe didn't exist before this one (as in, there wasn't a universe that collapsed before it)?

      Well, the earlier you get the more uncertain the theories get.
      I tell you, what I remember.
      First there was only energy. The energy in form of light yielded material. Two photons hitting on one another can create two particles of matter and anti-matter of equivalent energy (E=mc^2).
      Interestingly, our universe has is a certain assymmetry. Certain anti-matter particle have a shorter half-life than their matter counterparts.
      From the massive amounts of energy and the little discrepancy in half-life all matter was produced.

      But now, you certainly asks where does the energy and the space come from. But I guess you are not alone, as this is the question physics are discussing about. But before that, the earliest moments of the universe are still a point of research.

      The main question is, has this universe a causal beginning, or not.

      To understand the past one has to know the future :).

      If there is enough matter, the universe will contract and collapse, if there is not, the universe will expand until the end of time.

      The current known mass does not suffice to let the universe collapse, and IRC doesn't explain some other thinks. This is why people are searching for "dark matter". Some mass which is not visible.

      An ever expanding universe must have a beginning.
      This poses us with some questions: is there a "before" this universe, or did time came into existance with this universe. Is there another "dimension" where universes come into existance and vanish, and can we possibly understand it?
      Where from and why did it came into existance?

      An collapsing universe on the other hand could be the seed for another universe. This cycle can exists without a beginning and end.
      This version has obviously less open questions.

      --
      "Between strong and weak, between rich and poor [...], it is freedom which oppresses and the law which sets free"
    19. Re:And another thing by Yokaze · · Score: 1

      > IRC doesn't explain some other thinks
      IRC doesn't explain some other things.

      For example, my spelling mistakes. I know there others left, but this one makes the text hard to understand.

      --
      "Between strong and weak, between rich and poor [...], it is freedom which oppresses and the law which sets free"
    20. Re:And another thing by Nyphur · · Score: 1

      Laugh if you will, but keep this in mind as you titter: I'm a child. I have my entire life to clear up on things like this. You think they teach this kind of stuff to children? No way. I had to gather what I could from any place I can, which isn't easy. When you were a child, you probably didn't even know what half of those words meant and after you succumb to whatever form of death awaits you, I'll be here... stating a corrected quantum theory.

      --
    21. Re:And another thing by nomel · · Score: 1

      Thanks for the good explanation :)

      >> Was space a result of the big bang or something? Was distance?

      >Excactly. So, at one point in time, 10 miles from anywhere could mean 10 times through the universe and back to where you started through a universe with a mile diameter.

      I find this hard to understand. Why wouldn't 10 miles be in the nothingness that is next to the big bang? Why would it have to be limited to within the bigbang/growing universe(?)?

    22. Re:And another thing by Yokaze · · Score: 1

      > Why wouldn't 10 miles be in the nothingness that is next to the big bang? Why would it have to be limited to within the bigbang/growing universe(?)?

      If you walk for 10 miles, how far will you get? And what if you go on a circle of 1m diameter? Probably not farther than 1m. And what is if the circle has no diameter?

      It is similar with space. It has a diameter (the largest distance of any two points in it), because it is wrapped around.

      Except that the "circle" is 3 dimensional (or even more) and the diameter of the "circle" is growing. Once the diameter was probably a mere light second, or even a singularity, and now stretching over some light aeons.

      Don't try to visualise it in such high dimensions, our brains are not made for this. Instead stay on lower dimensions (circles, orb, tori).

      --
      "Between strong and weak, between rich and poor [...], it is freedom which oppresses and the law which sets free"
    23. Re:And another thing by meringuoid · · Score: 1
      I find this hard to understand. Why wouldn't 10 miles be in the nothingness that is next to the big bang? Why would it have to be limited to within the bigbang/growing universe(?)?

      For much the same reason that 'north' and 'south' are restricted to the Earth's surface, '10 miles' is restricted to the Universe. To speak of something as being '10 miles outside the Universe' is as meaningless as to speak of something being '10 miles north of the North Pole'.

      Warning: the analogy in this post is under tension comparable to that of cosmic string. Beware singularities and closed timelike curves.

      --
      Real Daleks don't climb stairs - they level the building.
    24. Re:And another thing by nomel · · Score: 1

      >"To speak of something as being '10 miles outside the Universe' is as meaningless as to speak of something being '10 miles north of the North Pole'."

      So, the universe was only the space inside the big bang, and as it grew, the space within that?

    25. Re:And another thing by nomel · · Score: 1

      Again, I think I'm visualising the "big bang" as a "big bang" of matter...just a ball (or whatever shape) of matter/energy with some amount of volume. It then expanded, increasing it's volume (relative to what it was before). So, outside the big bang would be a point that it would expand to a couple moments later.

      I probably have some conceptual flaw that's keeping me from even slightly understanding. Even if you are considering the universe as only what was contained in the big bang...but if so, I would still think that you could have a measure of distance past this (for the stated reasons above).

      Anything obviouse that I'm missing? :)

    26. Re:And another thing by BoogieChile · · Score: 1

      And that's something I've always wondered - if every point of the universe is expanding relative to every other point, does that mean everything is getting bigger?

      Or if it's that the points are getting further away, then is everything getting less dense?

  6. My curious cat by NanoGator · · Score: 4, Funny

    My cat performs gravitic experiments all the time. He's even discovered anti-gravity. He pushes my cell phone off the desk, and within minutes it levitates back up to the desk.

    --
    "Derp de derp."
    1. Re:My curious cat by Poofat · · Score: 1

      This is very, very true. I have always had suspicions that cats were put on the earth to test gravity by pushing things off desks, counters, tables and staying immobile in one spot for long periods of time.

  7. Re:Gravity doesn't effect me by Anonymous Coward · · Score: 1, Funny

    I should hope not, given that effect is not a verb!

  8. Gravity waves != gravitational waves by ControlFreal · · Score: 5, Informative

    Allright, IAAP (I Am A Psysicist), and I think it's good two debunk a common misconception here:

    Gravity waves are not the same as gravitational waves

    Gravity waves are matter density waves in fluidi (fluids or gases) caused by the interaction of two forces: bouyancy and gravity. Here, bouyancy is the upward-driving force, and gravity is the downward-driving force. The essence is that these waves require a medium to propagate (e.g. air).

    Gravity waves can be found in the atmosphere, e.g. clouds which form in regular bands of cloud and clear sky, where the gravity waves carry momentum and energy from the troposphere to the middle and upper atmosphere Gravity waves can also be found on the surface of fuilds: think of the waves behind a boat. A good primer on gravity waves can be found here

    Gravitational waves are a whole different ballgame! These waves have got nothing to do with matter densities as they don't require a medium to progagate: it is not matter that moves, and in that respect gravitational waves are like light (which, contrary to beliefs held at the beginnning of the century, don't require a medium such as "ether"). Gravitational waves are wacves in the spacetime-metric.

    So what the hell does that mean? Well, in gravity waves, there is a wave in space (and time) in which the thing that changes over space and time is the density of matter. In gravitational waves, there also is a wave in space and time, but the thing that "wiggles" is not the density of matter (or the strength of electric and magnetic fields, like in light or EM radiation in general), but the properties of the fabric of space and time itself. You can think of it as if the coordinate system itself wiggles, so to speak. This "wiggling" results in the length of the arms of e.g. the LIGO interferometer to change ever so slightly, causing a phase shift between light beams send through both arms, which can (hopefully) be detected.

    In more mathematical terms, the exact properties of space and time are called the metric. In a portion of space without any matter, the metric is flat (called the Minkovski metric), which means that the usual laws of geometry apply. In any circumstances with matter (and thus gravity) present, these laws to do hold up!

    What?!, I hear you think. Yes sir, you've been lied to in geometry class! However, you've been lied to only very, very slightly. Example: if you measure the radius of a sphere (say: R), you expect to find a surface area of exactly 4/3 * pi * R^3. If the earth would be a perfect sphere (which it isn't), and you would be able to measure its radius and surface very accurately, you would find that the surface area is ever so slightly smaller than expected. Or, in other words, the radius seems to be a bit too large (in the order of 3 cm or 30 cm IIRC). Read more about space time curvature here/

    A primer on gravitational waves can be found here. A more detailed description here.

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    1. Re:Gravity waves != gravitational waves by Anonymous Coward · · Score: 2, Funny
      What?!, I hear you think. Yes sir, you've been lied to in geometry class! However, you've been lied to only very, very slightly. Example: if you measure the radius of a sphere (say: R), you expect to find a surface area of exactly 4/3 * pi * R^3.

      When I finished geometry, I expected to find the surface area of a sphere to be exactly 4*pi*R^2.

    2. Re:Gravity waves != gravitational waves by ControlFreal · · Score: 1

      Ah crap, you're right of course... ;)

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      Support a Europe-related section on Slashdot!
    3. Re:Gravity waves != gravitational waves by nomel · · Score: 1

      Wouldn't these gravitational "wiggles" be caused by a change in mass density? Wouldn't that be the same as a gravity wave in a sense? Or can a gravitational wave be somewhat considered like being in the "far field" of an em wave, where the waves are their own entities, no longer effected by the source?

    4. Re:Gravity waves != gravitational waves by inertia187 · · Score: 1

      I've been waiting with baited breath to see what kind of imaging they can come up with using these methods. It's just like the invention of the radio telescope, but only more so.

      More Information

      --
      A programmer is a machine for converting coffee into code.
    5. Re:Gravity waves != gravitational waves by pyrrho · · Score: 2, Funny

      man, I HATE it when you subconsciouly do an integration! Arg!

      --

      -pyrrho

    6. Re:Gravity waves != gravitational waves by notfancy · · Score: 1

      Gravitational waves are waves in the spacetime-metric.

      Wouldn't that make the metric negative in the vicinity of the source? What is the meaning of that? Its theoretical consequences?

      Call me a Platonist if you will, but I'm under the impression that, if it's negative, it ain't a metric.

  9. I have a question. by Mac73117 · · Score: 2, Interesting

    Why couldn't we put this lab in orbit? That way we wouldn't have to compensate for so much extraneous gravitational noise. Or am I missing that fact that this equipment needs the Earth's gravity well to function.

    Disclaimer: I am not a physicists, just a guy who likes science.

    1. Re:I have a question. by Patrik_AKA_RedX · · Score: 2, Informative
      Why couldn't we put this lab in orbit? That way we wouldn't have to compensate for so much extraneous gravitational noise.
      That wouldn't matter. The amount of gravity affecting a orbiting spacecraft isn't much lower than on earths surface. The whole concept of orbiting requires gravity (the craft falls around the planet).
      Even far away from the planet the lab would still be inside the gravitational field of the sun.
      So to compensate for gravity you would need to place the lab in interstellar space, however it's much more practical to leave the lab on earth and compensate for the planet's gravity in the equations.
    2. Re:I have a question. by edgar_is_good · · Score: 2, Interesting

      There actually is a plan to put it in space called LISA. It would consist of satellites to study the waves. Different setups make you sensitive to different sources of gravitational waves and LISA will detect different sources than LIGO will.

    3. Re:I have a question. by PDAllen · · Score: 1

      We could. It'd help. Do you have $many-billion to spare putting equipment up that needs to be quite big?

    4. Re:I have a question. by Stuntmonkey · · Score: 2, Informative

      Why couldn't we put this lab in orbit?

      The main reason is that the effect is so weak. A mission concept called LISA is being studied by ESA and NASA. The idea is to have 6 spacecraft orbiting the Sun, which together form a interferometer several million kilometers in size. The catch: Because the waves are so weak, the distances between these spacecraft would need to be controlled to within about a nanometer (!) to have any hope of detecting a signal. Needless to say a VERY challenging mission.

      A lot of other interesting missions would be enabled by good formation flight technology. Look at NASA's Terrestrial Planet Finder mission, or the ESA's similar Darwin mission.

    5. Re:I have a question. by Thuktun · · Score: 1

      Why couldn't we put this lab in orbit? That way we wouldn't have to compensate for so much extraneous gravitational noise.

      Because "microgravity" does not mean "a minimum of gravity".

  10. Re:Gravity doesn't effect me by charlesbakerharris · · Score: 2, Informative

    Effect is a verb. He just used it incorrectly. To effect = to do, as in "he effected a change", whereas to affect = to alter.

  11. Re:Gravity doesn't effect me by Patrik_AKA_RedX · · Score: 1

    In Engrish every word can have every function you want it to have.

  12. Re:Gravity doesn't effect me by Lug+Monkeybird · · Score: 1

    So, in a sense, he was actually quite incorrect. Gravity is a prerequisite to solar system and thus planetary formation, which in turn was requisite to the emergence of life as we know it. Therefore, gravity did in fact effect him (and all of us), although in fairness it did so only once and no longer brings him into being. -- L

  13. Lost me towards the middle by Anonymous Coward · · Score: 1, Interesting

    The thrust of these new developments in gravity research implicates multiple dimensions as the cause for the relative weakness of gravity.

    And if they can make this idea self consistant and conform to measurements, good for them.

    But this has a feeling of sloppiness to it. ie: we cannot explain this coherently with 4 dimensions, so we take what we can't figure out and hide it within the complexities of additional dimensions.

    Could it be possible that explaining gravity is beyond the scope of our current models, and no amount of tap dancing is going to make it fit with their contexts?

    But you can't do that, no no no! Don't even bother pondering alternative models or colleagues will jump up and down on your skull, screaming "Crackpot!"

    There should be hundreds of small models competing with each other, not one huge massive lumbering model. Isn't there a science that studies scientific methods? This single model for everything is hitting a wall.

    There's a million different ways to self consistently model everything, some ways are easier to articulate than others. The only way to find out which ones the human mind can manipulate the easiest..is to experiment! Can't have any of that experimenting stuff, though. No way. Get labeled a crackpot and you're fucked. Bye bye career. Bye bye reputation.

    1. Re:Lost me towards the middle by edgar_is_good · · Score: 1

      Let's be clear about something: there are two issues relating to gravity which involve extra dimensions:

      1) How does one combine quantum mechanics and gravity?

      2) what is gravity so weak compared with the other forces?

      The first has only ever had one consistent theory, and that is string theory (or more recently the still somewhat ill-defined m-theory). superstring theory is the only current stable string theory and it is only a consistent quantum theory in 10 dimensions. (M-theory is a limit where you see a new, 11th dimension appear)

      Given that it requires additional dimensions, people assumed they were compact and with small radii so we couldn't see them.

      With respect to part two, there are four dimensional solutions to why gravity is weak compared to gravity, so one doesn't need extra dimensions to explain their hierarchy of gravity/strong-weak-electromagnetic strengths.

      However, if there are extra dimensions, if they were larger than the small size, then they can dilute the gravity. This was the big change in thinking in 98/99, when two proposals (large extra dimensions and warped extra dimensions) came on the scene. However, the exciting thing about them was precisely the fact that they _were_ testable! There was the hope of experimentally seeing additional dimensions and maybe string theory.

      While there sociological pressure to conform, these ideas were initially well out of the mainstream and took time before they were embraced as serious ideas by the community at large. They are now (although there are still detractors).

      So I don't know which you're objecting to: using extra dimensions to resolve the first or the second issue, but either way, both have proved as fruitful avenues for new ideas. Of course eventually every revolution turns into the status quo...

    2. Re:Lost me towards the middle by PDAllen · · Score: 1

      Could it be possible that explaining gravity is beyond the scope of our current models, and no amount of tap dancing is going to make it fit with their contexts? Probably. But you can't do that, no no no! Don't even bother pondering alternative models or colleagues will jump up and down on your skull, screaming "Crackpot!" String theory? Branes? No-one got seriously attacked over them. Everyone accepts that if current_model isn't working, you need a new model. Of course, if you're just spouting crap which doesn't make any sense (or isn't mathematically consistent) then you'll get dumped on, but produce an idea which might, or a set of equations which might/demonstrably do approximate to known models in low-energy situations and you're doing useful work. (if your equations do not approximate to GR in low energy situations, then everyday life proves them wrong, in the same way that GR approximates to special relativity when there's not too much mass around, and that to Newton's laws when energies are low). There are a few models competing; your 'lumbering big one' is simply the model that's been fairly effective in the past and hasn't been completely blown to bits yet (but probably isn't correct), and various newer models are being considered. If you want hundreds of models, though, you have to think of hundreds of radically new ideas which still produce real-life results in real-life situations. This is not easy. I take it you've never tried anything much beyond pop-sci and high school physics, or you would know that.

  14. Re:Gravity doesn't effect me by kannibal_klown · · Score: 1

    Affect = to change Effect = the result

  15. Frame of Reference by Geekwad · · Score: 1

    Now wait a minute .. how can these guys be sure that when their mirrors are distorted, that the laser emitters they're using to measure them are not also distorted .. therefore giving them whacky data?

    --

    - http://pakman.sytes.net/
  16. Re:Gravity what it is and what it is not. by DoctorRad · · Score: 2, Informative
    The eminent professor asked the Batchelor student to explain General Relativity. The student thought for a moment before replying "Well, I'm sure I understood it at some point, sir, but I appear to have forgotten".

    The professor looked startled: "This is an unfortunate turn of events. It appears that of the two people in the world ever to have understood General Relativity, one of them has forgotten".

    Anyway, thing is, General Relativity is all about the fact that the presence of mass causes the curvature of space-time. What we call gravity is a consequence of that curvature.

    Get your head around that one, and we'll talk some more.

    Matt...

    --

    Save the Bottom Line
  17. Re:Gravity what it is and what it is not. by R1ch4rd · · Score: 1

    I think the way the theory goes is: mass causes gravity which causes space-time curvature.
    It's not space-time curvature that holds us on Earth, it's gravity.
    Einstein found out that there are other effects of gravity which can only be explained if gavity causes a curvature of space-time.

    I'm not a physisist, but I like this part of science.

  18. Re:Gravity doesn't effect me by sbszine · · Score: 1

    Affect = to change Effect = the result

    Also effect = to bring about (e.g. 'to effect change' as distinct from 'to affect change', i.e. to influence the type of change). And also, affect = to take on (e.g. 'to affect a lisp').

    --

    Vino, gyno, and techno -Bruce Sterling

  19. Re:Gravity what it is and what it is not. by edgar_is_good · · Score: 2, Informative

    No, no, gravity is just spacetime curvature and spacetime curvature holds us on the Earth.

  20. Re: Gravity doesn't effect me by ChozCunningham · · Score: 1

    I Soviet Russia, gravity affects you. Oh, wait...

    --
    Looks good for your age..
  21. PSU Gravity Wave research by Auriam · · Score: 1

    Yes, I've noticed that PSU is doing some very good work with LIGOS as well.. there's a mysterious little nondescript door on the 2nd floor of my physics dept, a little brown door with the words 'Center for Gravitational Wave Research' stenciled neatly in old-fashioned letters on the frosted glass.. asked my physics prof about it and he confirmed that PSU is indeed one of the forefront institutions working on it.. I'm going to have to find a way to wiggle my way into helping them out with it ;)

  22. Re:Pretender? by mike3411 · · Score: 1

    critisizing is one thing, if you think it's so bad, why don't you point us in the direction of a better explanation?
    although given you're posting as AC i'd say there's a 50/50 chance your post is total nonsense : P

    --
    Mod me down, and I will become more powerful than you can possibly imagine!
  23. Are you kidding? by Thuktun · · Score: 1

    You gotta wonder what gets these people out of bed day in and day out.

    I'd love to get paid for 30 years to continually look for something and not get canned for failing to deliver.